Solomon Islands

Volcano
Hazard level:
High

In the area you have selected (Solomon Islands) volcanic hazard is classified as high according to the information that is currently available. This means that the selected area is located at less than 50 km from a volcano for which a potentially damaging eruption has been recorded in the past 2,000 years and that future damaging eruptions are possible. Based on this information, the impact of volcanic eruption must be considered in all phases of the project, in particular during project design, implementation and maintenance. Further detailed information should be obtained to adequately account for the level of risk posed by individual volcanoes.

Recommendations

EARLY WARNING ACTION: Ensure the project can act on volcanic early warnings. This may involve having a plan in place to mobilize in the event of a warning being received.
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Volcanic eruptions can have long lead in times, which can allow pre-event warnings. This can then allow measures to be taken to protect vulnerable systems or components.

Some countries are able to provide ashfall warnings, based on modelling of ash dispersion. Contact the local volcano observatory or geological hazards agency, if available, for information about ashfall warnings.

Some countries are able to provide lahar warnings. Contact the local volcano observatory or geological hazards agency, if available, for information. The World Organisation of Volcano Observatories (WOVO) provides a semi-regularly updated list of global volcano observatories, including the volcanoes they monitor and their contact details. This can be accessed at: http://www.wovo.org/observatories/

Link to early warning systems to enable project to be shut down.

Consider developing procedures that will enable project to shut down during a hazard event to minimize damage – especially for critical infrastructure projects.

If warranted, consider developing a specific early warning system for the project.

Work out how to contact any local volcano observatory in the event of an eruption crisis and at project planning stage. Make sure they know about your project and any significant vulnerabilities to volcanic hazards you identify, with a way to contact you in a crisis.

IMPACT: Consider the effect that potentially lethal and destructive volcanic hazards near to the volcano – ballistic projectiles, lava flows, lahars and pyroclastic flows – could have on the planned project. Lahars can impact areas within valleys as far as 100 km from a volcano. Further information should be gained from local volcanic hazard maps, if available.
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A challenge for volcanic risk assessment is that eruptions can produce multiple hazards. These can occur either in sequence or simultaneously; travel at speeds ranging from very slow (lava flows) to very fast (pyroclastic density currents); and affect different areas around the volcano.
Potentially-lethal and destructive hazards near to the volcano include pyroclastic density currents/flows; lahars; ballistic projectiles; lava flows; volcanic landslides; earthquakes and tsunami. Thick ashfalls may also occur close to the volcano.

Take steps to understand the distribution of the multiple hazards that a volcanic eruption may trigger.

Consider both the likelihood of these hazards occurring, and their consequences for the project. If the risk is unacceptably high over the expected operational life of the project, consider moving its location.

Volcanic hazard maps

Volcanic hazard maps and indigenous knowledge are an excellent planning resource if available.

They commonly depict areas exposed to specific hazards such as lahars and ballistic projectiles, for individual volcanoes.

Hazard maps may indicate the long-term potential from a range of eruptions and hazards, or may focus on a scenario – be sure to look into the wider context and potential range of hazards, if a hazard map appears to focus on only one aspect or scenario.

If possible, contact the in-country volcano observatory or geological hazards agency to determine the availability of hazard maps relevant to the project site. Contact details are available at: http://www.wovo.org/observatories/

Other sources of information may include university earth science departments or international organizations such as the United Nations and the World Bank.

Bear in mind that the project site may be exposed to hazards from multiple volcanoes.

Determining project location

Near-volcano hazards such as pyroclastic flows, lava flows and ballistic projectiles are in general highly destructive, and few effective structural mitigation methods are available.

There are no widely adopted volcanic building codes or building performance guidelines to regulate infrastructure design in volcanic hazard zones. Rather, land-use planning is the primary tool for hazard avoidance.

Consult any available volcanic hazard maps and indigenous knowledge to ensure that the project location avoids known hazard zones for highly destructive hazards such as pyroclastic flows.

Contact local authorities to find out about any land-use zoning maps for the project area.

Be aware of the potential for hazards near to the volcano to affect project support systems such as roads, bridges, water systems and power transmission and distribution poles.

Be aware also of the potential for lahars to affect project support systems such as water supply systems, roads, bridges, power transmission and distribution poles, as lahars can travel distances of over 100 km from the volcano.

Structural mitigation options for specific hazards

There are no structural mitigation options available for pyroclastic density currents.

For lahars, options include reinforcing of bridge piers and the construction of diversion berms.

For ballistic projectiles, limited structural mitigation options are available. Purpose-designed ballistic shelters (usually steel-reinforced concrete bunkers) are sometimes used in high-hazard areas where warnings are not possible), although avoidance is usually preferable.

For lava flows, avoidance is the widely preferred option, although some success under crisis conditions has been achieved with diversion structures such as berms.

For ashfall, options may include strengthening structures to ashfall loading and developing protective structures to minimize ash entry into sensitive systems and/or buildings.

Additional (non-structural) mitigation options

Consider incorporating operational plans and procedures into project to increase resilience to volcanic hazards. There may be additional benefits in decreasing time needed for restoration and recovery.

Risk transfer mechanisms such as insurance should be considered. These could include purchasing insurance for reconstruction and replacement of damaged assets, clean-up costs, and business interruption/continuity insurance.

Shut-down of vulnerable systems to minimize impacts on projects may be a good mitigation option for some volcanic hazards. This option is likely to be particularly effective if linked to warning systems. An example from New Zealand is the Eastern Ruapehu Lahar Alarm and Warning System (ERLAWS) which uses three separate lahar sensors high on the mountain to alert response agencies and trigger barrier gates, warning lights and electronic signs at key road and rail bridges.

Managing life safety risks

Plan and exercise for evacuation and shelter

Ensure the project receives early warning messages from existing systems.

If the risk is considered high enough, and warning is possible, plan and exercise for staff evacuation and sheltering arrangements.

This may involve development of evacuation routes and provision of welfare materials at safe locations.

Exercise the arrangements at least annually, or more frequently to allow for new staff arrival.

If sheltering, provide appropriate protective gear.

The following study is open access and summarises known impacts of a range of volcanic hazards on critical infrastructure.

REGULATIONS: Check with local authorities for any local regulations concerning volcanic hazards. Ensure that the project conforms to 1) any applicable volcanic hazard land use planning regulations; 2) any existing plans for warning and evacuation; and 3) any national laws, regulations and rules.
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While hazard-specific regulations exist for some hazards such as earthquakes (seismic building codes), it is rare to have volcano-specific regulations. Volcanic hazards are usually managed by generic disaster management, natural hazard planning, and health and safety regulations.

Ensure project conforms with all laws, regulations, rules and guidance for land-use planning and building design codes.

Ensure project conforms with all laws, regulations, rules and guidance for health and safety.

TECHNICAL EXPERTISE: Engage a qualified local or international volcanologist to investigate the volcanic hazards in the project area in more depth. Where possible, establish a relationship with the local volcano observatory/agency.
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Engage an expert to conduct a volcanic hazard assessment for project area

Pyroclastic density currents (sometimes called pyroclastic flows): these are fast-moving clouds of hot gases and particles, formed by the collapse of an eruption column or the explosive interaction of magma with water (ground or surface). They travel very rapidly, at speeds >350 km/hr, down the sides of the volcano and can extend out to tens of km from the vent. They are highly lethal (from both heat and pressure/impact) and destructive to most structures.

Lahars (volcanic mudflows): these are flows of volcanic debris-laden water which travel downslope under gravity and thus follow river valleys. They can travel far (100 km or more) from the volcano. It is important to note that lahars can also be triggered during non-eruptive times, e.g., by crater lake breakout events, or by heavy rainfall onto unconsolidated material from previous eruptions.

Ballistic projectiles: these are fragments of lava or rocks from around the vent of the volcano which are violently ejected from the volcano and follow ballistic trajectories. They may be both lethal and destructive, but are usually limited to within a few km of the vent.

Ash: Volcanic ash consists of fragments of rock that become airborne during a volcanic eruption. The general term for all such material is ‘tephra’, with ‘ash’ constituting the material less than 2 mm in size. Ash is dispersed downwind, and can be carried hundreds or even thousands of kilometres away from the volcano, and cover large areas of land with ashfalls.

Gas: Volcanoes can emit gases not only during eruptions, but also between eruptions. Volcanic gases are dispersed downwind and may travel hundreds or even thousands of kilometers. The main gases emitted by volcanoes are water vapour, carbon dioxide and sulphur dioxide. Of these, sulphur dioxide (SO2) has the greatest consequences for people and infrastructure due to its ability to form sulphuric acid droplets.

Lava flows: outpourings of molten magma from volcanic vents or fissures. They typically move slowly, thus tend to be destructive rather than lethal. Avoidance is generally the best mitigation option, but there are also examples of successful attempts to stall or divert advancing lava flows. It is important to note that these measures usually only buy time to delay the onset of lava inundation.

Sector collapse: volcanoes are often unstable landforms, and even after long periods of inactivity, may suddenly collapse to produce landslides. This may be more common for volcanoes that are closely linked to tectonic faults; collapse is often triggered by earthquakes or volcanic events. Slopes that have been altered by weathering and/or hydrothermal activity may be more prone to collapse.

Tsunami can be triggered by volcanic eruptions, usually due to landslides displacing large volumes of water, or when eruptions occur beneath large water bodies. Whilst rare, they account for some of the largest losses of life during volcanic eruptions.

A volcanic hazard assessment should use a systematic methodology to evaluate credible hazards and ensure that all relevant hazards are included in the analysis. This should include taking steps to understand the distribution of the multiple hazards that a volcanic eruption may trigger. Refer to any local volcanic hazard maps, if available. The volcanic hazard assessment should consider the following background information:

Volcanic events rarely produce just a single dangerous hazard. Eruptions usually initiate a complex sequence of events that can produce a wide range of eruption products and hazards.

These hazards can occur in sequence or simultaneously; travel at speeds ranging from very slow (lava flows) to very fast (pyroclastic density currents); and affect different areas around the volcano.

Even areas tens to hundreds of kilometres away from a volcano can be affected by volcanic hazards, including volcanic ash and gases, lahars and tsunami.

Episodes of eruptive activity at individual volcanoes can last from hours to decades, or longer and there can be periods of months or years between phases of activity.

Volcanic regions often have multiple closely-spaced active volcanoes, which increases the likelihood of a nearby site being affected by volcanic hazards.

Some volcanic hazards can occur during non-eruptive periods. For instance, lahars can be triggered by heavy rainfall onto unconsolidated material from previous eruptions.

There is a relationship between the size and frequency of eruptions. Larger eruptions tend to be less frequent but have more major impacts. Smaller eruptions tend to occur more frequently, but with more minor impacts.

Smaller eruptions may be more difficult to forecast as they have fewer warning signs.

All active volcanoes have the potential to erupt again, sometimes with very little warning. Some volcanoes have erupted after lying dormant for thousands of years or longer.

Consider whether local site conditions (e.g. topography and prevailing wind direction) could increase the exposure of the project site to volcanic hazards. For instance, projects located in valleys may be subject to lahar hazards, even at distances of >100 km from the volcano.

If the project is in a hazardous zone, collect more specific volcanic hazard data for the exact project location. This could start with performing volcanic hazard modelling for the range of possible volcanic threats to the project site (i.e. develop site-specific volcanic hazard assessment model).

For more information on global volcanic hazards and volcanic hazard assessment, please refer to :

Contact organisations that may have knowledge of volcanic hazards in the area: local governmental civil protection, scientific organisations and indigenous communities.

Volcano Observatories

Some countries with active volcanoes have volcano observatories and/or agencies responsible for monitoring local volcanoes and carrying out hazard assessments – to varying extents. If possible, establish a working relationship with the national or local volcano observatory or agency. If a national or local observatory/agency does not exist contact one of the regional or global organizations.

These organisations typically have responsibility for provision of volcanic hazard information and monitoring of eruptive activity to inform warnings to exposed communities. They usually have a good understanding of the range, extent and intensity of hazards which can be produced by the local active volcanoes. They can also be an excellent point of contact for accessing local volcanic hazard information and local/national emergency management/civil protection information and contacts.

The World Organisation of Volcano Observatories (WOVO) provides a semi-regularly updated list of global volcano observatories, including the volcanoes they monitor and their contact details. This can be accessed at: http://www.wovo.org/observatories/

Utilise traditional knowledge to increase understanding of volcanic risk in project area

Traditional and indigenous knowledge can contribute to understanding volcanic risk, especially when the geological or written history of a volcano is limited. Indigenous communities often have their own understanding and ways of articulating a volcano’s processes. They may also have traditional systems of land use planning and emergency management practices.

Utilise local knowledge to increase resilience of project

Consider contacting local or international staff with experience of working in the project area to understand how they have sought to reduce volcanic risk. Previous or other current projects may have already considered the volcanic hazard assessment and risk management approaches required for this region.

IMPACT FAR FROM HAZARD SOURCE: Consider the effects of volcanic ashfall and gases on the project. These hazards are the most far-reaching of the volcanic hazards and can affect areas hundreds or even thousands of kilometers downwind of volcanoes.
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Over 90% of all volcanic eruptions produce volcanic ash. Volcanic ash consists of fragments of rock that become airborne during a volcanic eruption. The general term for all such material is ‘tephra’, with ‘ash’ constituting the material less than 2 mm in size.

Ash is dispersed by prevailing winds away from the volcano. Ash particles can be carried hundreds or even thousands of kilometres away from the volcano, and can cover large areas of land with ashfalls.

Very thick falls can cause structural damage to buildings (e.g. roof collapse) leading to casualties. Casualties may also be indirectly sustained, for example during ash clean-up operations or in traffic accidents.

Ashfalls can also cause a public health hazard, with the short-term health effects of ash exposure typically being irritation of the eyes and upper airways and exacerbation of pre-existing asthma.

Ashfalls can also disrupt critical infrastructure services (e.g. electricity and water supply, aviation and other transport routes), damage buildings, and damage or disrupt agricultural production and other economic activities.

If the project is related to agriculture, consult local agricultural agencies for advice on managing impacts to agricultural production.

Even relatively thin ashfalls of a few millimetres can cause significant societal impacts, through widespread damage, disruption and economic loss.

Impacts can be long-lived, either because eruptions may be long-duration or because ashfalls may be remobilised by wind, water, traffic or human activities.

Thin ashfalls are generally disruptive rather than destructive, and many ash impacts can be successfully anticipated and mitigated against.

Ash is extremely abrasive, and can cause severe damage to assets such as hydroelectric power generation turbines, pump impellers and bearings in motors. Take all possible steps to protect equipment such as closing water intakes and protectively shutting down pumps and motors, if possible.

Ash clean-up can be time-consuming and expensive. Pre-event planning can help save time and expense by considering personnel and equipment requirements, identification of potential disposal sites and strategies for stabilising ash deposits.

Develop ash management plans, including provisions for clean-up and protocols to prevent ash ingress into buildings.

Consider the frequency and related possible consequences from volcanic ash hazards by reading these resources and learning about nearby and regional volcanoes. Plan measures based on the resources for rapid response if you consider that the chance of impact will be sufficiently disruptive.

Volcanic gases

Volcanoes can emit volcanic gases not only during eruptions, but also between eruptions.

Volcanic gases are dispersed downwind and may travel hundreds or even thousands of kilometres.

The main gases emitted by volcanoes are water vapour, carbon dioxide and sulphur dioxide. Of these, sulphur dioxide (SO2) has the greatest consequences for people and infrastructure due to its ability to form sulphuric acid droplets.

If possible, contact the local volcano observatory or geological hazards agency to determine whether volcanic gas hazards are present in the project area.

Consult local agencies and community leaders to find out about gas hazards in the project area.

If the project is related to agriculture, consult local agricultural agencies for advice on appropriate crop types that may be more resistant to the effects of acidic gases.

Be aware that metal components and fittings may be subjected to accelerated corrosion. It may be possible to replace them with more resistant materials such as stainless steel.

Health and safety considerations

Understand legal health and safety obligations to workers at the project and ensure that the project has appropriate procedures to meet these.

These obligations vary between countries and organizations.

Understand implications of working in environments where ash and/or gas hazards may be present:

Common issues associated with ashfall include

exposure to fine airborne ash

slips and falls during ash cleanup operations, particularly from roofs and ladders

strain injuries from moving heavy ash

increased risk of traffic accidents due to loss of visibility and traction and coverage of road markings

Acid-forming volcanic gases such as sulphur dioxide are irritating to eyes, throats and respiratory tract, with asthmatic individual being highly sensitive.

Provide personal protective equipment for personnel working in hazardous environments.

For further, comprehensive information on volcanic health hazards and advice on dust and gas masks and personal protective equipment, see the website of the International Volcanic Health Hazard Network